tenekon.commandline.extensions.polytype

Tenekon.CommandLine.Extensions.PolyType

Tenekon.CommandLine.Extensions.PolyType adds an attribute-driven layer on top of System.CommandLine, powered by PolyType shape generation. You define commands, options, and arguments with attributes, and get fast, strongly-typed binding without runtime reflection. It supports class commands and function commands and is trimming/AOT friendly.

[!NOTE] This project was crafted in a very short time. The public API is intended to be stable, but changes may occur as the library matures.

Install

dotnet add package Tenekon.CommandLine.Extensions.PolyType

Table of Content

• Prerequisites
• Quick Start (Class-Based)
• Quick Start (Function-Based)
• Concepts at a Glance
• Defining Commands
• Defining Options and Arguments
• Defining Directives
• Handler Methods and Signatures
• Method Commands (Instance Methods)
• Interface-Based Specs
• Naming Rules and Aliases
• Requiredness and Arity
• Validation and Allowed Values
• Runtime Creation
• Runtime Creation: Class-Based
• Runtime Creation: Custom ITypeShapeProvider
• Runtime Creation: Model-First (Advanced)
• Runtime Creation: Function-Based
• Parsing Without Invocation
• Binding Results and Helpers
• Invocation Options (Per Call)
• CommandRuntimeContext
• Services and Service Resolution
• Functions and Function Resolution
• Settings (CommandRuntimeSettings)
• Response Files and POSIX Bundling
• Built-In Directives
• File System Abstraction (Advanced)
• Trimming and AOT

Prerequisites

• Use PolyType source generation via [GenerateShape(IncludeMethods = MethodShapeFlags.PublicInstance)] and [GenerateShapeFor(IncludeMethods = MethodShapeFlags.AllPublic)].
• Command types must be partial.
• Target any project that can reference netstandard2.0 (the package also ships net10.0).

Quick Start (Class-Based)

Program.cs:

using Tenekon.CommandLine.Extensions.PolyType.Runtime;

return CommandRuntime.Factory.Object
    .Create<RootCommand>(
        settings: null,
        modelRegistry: null,
        modelBuildOptions: null,
        serviceResolver: null)
    .Run(args);

Command type:

using PolyType;
using PolyType.SourceGenModel;
using Tenekon.CommandLine.Extensions.PolyType.Spec;
using Tenekon.CommandLine.Extensions.PolyType.Runtime;

[GenerateShape(IncludeMethods = MethodShapeFlags.PublicInstance)]
[CommandSpec(Description = "Root command")]
public partial class RootCommand
{
    [OptionSpec(Description = "Greeting target")]
    public string Name { get; set; } = "world";

    [ArgumentSpec(Description = "Input file")]
    public string? File { get; set; }

    public int Run(CommandRuntimeContext context)
    {
        if (context.IsEmptyCommand())
        {
            context.ShowHelp();
            return 0;
        }

        Console.WriteLine($"Hello {Name}");
        Console.WriteLine($"File = {File}");
        return 0;
    }
}

Quick Start (Function-Based)

Program.cs: Preparation:

using PolyType;
using Tenekon.CommandLine.Extensions.PolyType.Spec;

[GenerateShapeFor(typeof(GreetCommand))]
public partial class CliShapes;

[CommandSpec(Description = "Greets from a function")]
public delegate int GreetCommand([OptionSpec] string name);

[!TIP] GenerateShapeForAttribute supports glob pattern

[!NOTE] Function commands require a function instance. Register it via runtime.FunctionRegistry or provide a custom ICommandFunctionResolver.

using Tenekon.CommandLine.Extensions.PolyType.Runtime;

var runtime = CommandRuntime.Factory.Function.Create<GreetCommand, CliShapes>(
    settings: null,
    modelRegistry: null,
    modelBuildOptions: null,
    serviceResolver: null);

runtime.FunctionRegistry.Set<GreetCommand>(name =>
{
    Console.WriteLine($"Hello {name}");
    return 0;
});

return runtime.Run(args);

Explicit:

using PolyType;
using PolyType.Abstractions;
using Tenekon.CommandLine.Extensions.PolyType.Runtime;

var shape = (IFunctionTypeShape)TypeShapeResolver.Resolve<GreetCommand>();
var provider = shape.Provider;

var runtime = CommandRuntime.Factory.Function.Create(
    commandType: typeof(GreetCommand),
    commandTypeShapeProvider: provider,
    settings: null,
    modelRegistry: null,
    modelBuildOptions: null,
    serviceResolver: null);

runtime.FunctionRegistry.Set<GreetCommand>(name =>
{
    Console.WriteLine($"Hello {name}");
    return 0;
});

return runtime.Run(args);

Concepts at a Glance

• Spec attributes describe commands, options, arguments, and directives.
• Model (Advanced) represents the metadata graph derived from shapes.
• Runtime builds System.CommandLine commands and binders from the model.
• Binding maps parsed tokens to strongly-typed objects.
• Invocation runs handlers with services and functions resolved.

Defining Commands

Use [CommandSpec] on classes to define commands.

Nested child commands:

[CommandSpec(Name = "git", Description = "Root command")]
public partial class GitCommand
{
    [CommandSpec(Name = "status")]
    public partial class StatusCommand
    {
        public int Run() => 0;
    }
}

Explicit parent/child linkage:

[CommandSpec(Description = "Root", Children = new[] { typeof(StatusCommand) })]
public partial class RootCommand { }

[CommandSpec(Parent = typeof(RootCommand), Description = "Child")]
public partial class StatusCommand { }

You can also control unmatched tokens with TreatUnmatchedTokensAsErrors on [CommandSpec].

Defining Options and Arguments

Property-based definitions:

[CommandSpec]
public partial class BuildCommand
{
    [OptionSpec(Description = "Configuration")]
    public string? Configuration { get; set; }

    [ArgumentSpec(Description = "Project path")]
    public string Project { get; set; } = "";

    public int Run() => 0;
}

Parameter-based definitions:

[CommandSpec]
public partial class CleanCommand
{
    public int Run([OptionSpec] bool force, [ArgumentSpec] string path) => 0;
}

OptionSpecAttribute and ArgumentSpecAttribute support:

• Name, Description, Hidden, Order
• Arity, Required
• AllowedValues
• ValidationRules, ValidationPattern, ValidationMessage

OptionSpecAttribute also supports:

• Alias, Aliases, HelpName
• Recursive
• AllowMultipleArgumentsPerToken

Defining Directives

Define directives with [DirectiveSpec] on properties or parameters. Supported types are bool, string, and string[].

[CommandSpec]
public partial class AnalyzeCommand
{
    [DirectiveSpec(Description = "Enable verbose diagnostics")]
    public bool Verbose { get; set; }

    public int Run() => 0;
}

Handler Methods and Signatures

Supported handler signatures:

• void Run() and int Run()
• Task RunAsync() and Task<int> RunAsync()

Optional parameters:

• CommandRuntimeContext as the first parameter
• CancellationToken as the last parameter
• Any other parameters resolve as services or functions

Method Commands (Instance Methods)

Public instance methods annotated with [CommandSpec] become child commands.

[CommandSpec]
public partial class ToolCommand
{
    [CommandSpec(Description = "Clean outputs")]
    public int Clean([OptionSpec] bool force) => 0;
}

Interface-Based Specs

Attributes can live on interfaces when the shape is generated with [GenerateShapeFor].

public interface IHasVerbosity
{
    [OptionSpec(Description = "Verbose output")]
    bool Verbose { get; set; }
}

[GenerateShape(IncludeMethods = MethodShapeFlags.PublicInstance)]
[GenerateShapeFor(typeof(IHasVerbosity))]
[CommandSpec]
public partial class InfoCommand : IHasVerbosity
{
    public bool Verbose { get; set; }
    public int Run() => 0;
}

Naming Rules and Aliases

• Names are auto-generated from type/member names.
• Common suffixes like Command, Option, and Argument are stripped.
• Names default to kebab-case.
• Options get long and short forms by default.

Override naming in [CommandSpec]:

[CommandSpec(
    Name = "init",
    Alias = "i",
    NameAutoGenerate = NameAutoGenerate.None,
    NameCasingConvention = NameCasingConvention.KebabCase)]
public partial class InitializeCommand { }

Requiredness and Arity

Requiredness and arity can be explicit or inferred from nullability and defaults.

[CommandSpec]
public partial class DeployCommand
{
    [OptionSpec(Required = true)]
    public string Environment { get; set; } = "";

    [ArgumentSpec(Arity = ArgumentArity.OneOrMore)]
    public string[] Targets { get; set; } = [];
}

Validation and Allowed Values

ValidationRules supports common file, directory, path, and URL rules. You can also provide a regex with ValidationPattern and a custom ValidationMessage.

[CommandSpec]
public partial class ScanCommand
{
    [ArgumentSpec(
        ValidationRules = ValidationRules.ExistingFile | ValidationRules.LegalPath,
        ValidationMessage = "Input must be an existing file")]
    public string Input { get; set; } = "";
}

Runtime Creation

Use CommandRuntime.Factory.Object for class-based commands and CommandRuntime.Factory.Function for function commands.

Runtime Creation: Class-Based

var runtime = CommandRuntime.Factory.Object.Create<RootCommand>(
    settings: null,
    modelRegistry: null,
    modelBuildOptions: null,
    serviceResolver: null);

Runtime Creation: Custom ITypeShapeProvider

using PolyType.Abstractions;

var shape = (IObjectTypeShape)TypeShapeResolver.Resolve<RootCommand>();
var provider = shape.Provider;

var runtime = CommandRuntime.Factory.Object.Create(
    commandType: typeof(RootCommand),
    commandTypeShapeProvider: provider,
    settings: null,
    modelRegistry: null,
    modelBuildOptions: null,
    serviceResolver: null);

Runtime Creation: Model-First (Advanced)

using PolyType.Abstractions;
using Tenekon.CommandLine.Extensions.PolyType.Model;

var shape = (IObjectTypeShape)TypeShapeResolver.Resolve<RootCommand>();
var provider = shape.Provider;

var registry = new CommandModelRegistry();
var model = registry.Object.GetOrAdd(
    typeof(RootCommand),
    provider,
    new CommandModelBuildOptions { RootParentHandling = RootParentHandling.Ignore });

var runtime = CommandRuntime.Factory.Object.CreateFromModel(
    model,
    settings: null,
    serviceResolver: null);

Runtime Creation: Function-Based

using PolyType.Abstractions;

var shape = (IFunctionTypeShape)TypeShapeResolver.Resolve<GreetCommand>();
var provider = shape.Provider;

var runtime = CommandRuntime.Factory.Function.Create(
    commandType: typeof(GreetCommand),
    commandTypeShapeProvider: provider,
    settings: null,
    modelRegistry: null,
    modelBuildOptions: null,
    serviceResolver: null);

Parsing Without Invocation

var result = runtime.Parse(args);
if (result.ParseResult.Errors.Count > 0)
{
    // handle errors
}

var instance = result.Bind<RootCommand>();

Binding Results and Helpers

var called = result.BindCalled();
var all = result.BindAll();
var isCalled = result.IsCalled<RootCommand>();
var hasRoot = result.Contains<RootCommand>();

if (result.TryGetBinder(typeof(RootCommand), typeof(RootCommand), out var binder))
{
    binder(instance, result.ParseResult);
}

Invocation Options (Per Call)

var options = new CommandInvocationOptions
{
    ServiceResolver = new MyServiceResolver(),
    FunctionResolver = new MyFunctionResolver()
};

return runtime.Run(args, options);

CommandRuntimeContext

CommandRuntimeContext provides:

• ParseResult
• IsEmptyCommand()
• ShowHelp()
• ShowHierarchy()
• ShowValues()

public int Run(CommandRuntimeContext context)
{
    if (context.IsEmptyCommand())
    {
        context.ShowHelp();
        return 0;
    }

    context.ShowValues();
    return 0;
}

Services and Service Resolution

ICommandServiceResolver provides constructor and handler dependencies that are not bound as options, arguments, or directives.

public sealed class ServiceProviderResolver(IServiceProvider provider) : ICommandServiceResolver
{
    public bool TryResolve<TService>(out TService? value)
    {
        value = (TService?)provider.GetService(typeof(TService));
        return value is not null;
    }
}

var runtime = CommandRuntime.Factory.Object.Create<RootCommand>(
    settings: null,
    modelRegistry: null,
    modelBuildOptions: null,
    serviceResolver: new ServiceProviderResolver(serviceProvider));

Functions and Function Resolution

Function instances are resolved separately from services. The resolution order is:

• CommandInvocationOptions.FunctionResolver
• CommandRuntime.FunctionRegistry and CommandRuntimeSettings.FunctionResolvers
• ICommandServiceResolver if AllowFunctionResolutionFromServices is enabled

[!IMPORTANT] Service resolution for functions only happens when AllowFunctionResolutionFromServices is enabled.

Register a function instance:

runtime.FunctionRegistry.Set<GreetCommand>(name =>
{
    Console.WriteLine($"Hello {name}");
    return 0;
});

Custom function resolver:

public sealed class MyFunctionResolver : ICommandFunctionResolver
{
    public bool TryResolve<TFunction>(out TFunction value)
    {
        if (typeof(TFunction) == typeof(GreetCommand))
        {
            value = (TFunction)(object)(GreetCommand)(name => 0);
            return true;
        }

        value = default!;
        return false;
    }
}

Settings (CommandRuntimeSettings)

Common settings:

• EnableDefaultExceptionHandler
• ShowHelpOnEmptyCommand
• AllowFunctionResolutionFromServices
• EnableDiagramDirective
• EnableSuggestDirective
• EnableEnvironmentVariablesDirective
• Output, Error
• FileSystem (Advanced)
• FunctionResolvers
• EnablePosixBundling
• ResponseFileTokenReplacer

var settings = new CommandRuntimeSettings
{
    ShowHelpOnEmptyCommand = true,
    EnableSuggestDirective = true
};

Response Files and POSIX Bundling

using System.CommandLine.Parsing;

var settings = new CommandRuntimeSettings
{
    EnablePosixBundling = true,
    ResponseFileTokenReplacer = static (Token token, out string[]? replacements) =>
    {
        replacements = null;
        return false;
    }
};

Built-In Directives

Configure built-in directives with:

• EnableDiagramDirective
• EnableSuggestDirective
• EnableEnvironmentVariablesDirective

File System Abstraction (Advanced)

Validation rules use IFileSystem. Provide your own implementation if needed.

public sealed class InMemoryFileSystem : IFileSystem
{
    public IFileSystemFile File { get; } = new InMemoryFile();
    public IFileSystemDirectory Directory { get; } = new InMemoryDirectory();
    public IFileSystemPath Path { get; } = new InMemoryPath();

    private sealed class InMemoryFile : IFileSystemFile
    {
        public bool FileExists(string path) => false;
    }

    private sealed class InMemoryDirectory : IFileSystemDirectory
    {
        public bool DirectoryExists(string path) => false;
    }

    private sealed class InMemoryPath : IFileSystemPath
    {
        public char[] GetInvalidPathChars() => [];
        public char[] GetInvalidFileNameChars() => [];
    }
}

Trimming and AOT

PolyType source generation allows runtime binding without reflection, making this library trimming-friendly and suitable for Native AOT scenarios.